Intraoperative localization of an epileptogenic focus with alfentanil and fentanyl

We evaluated the effectiveness of alfentanil and fentanyl in stimulating ep ileptogenic activity during surgery for intractable temporal lobe epilepsy under general anesthesia. Ten patients received a standardized anesthetic i nduction with IV fentanyl 5 mu g/kg, propofol 3-5 mg/kg, and atracurium 0.5 mg/kg. Maintenance was with isoflurane, 70% N2O/30% O-2, and an atracurium infusion. After dural opening, droperidol 0.02 mg/kg was administered IV. Both inhaled anesthetics were discontinued and verified to be at 0 end-tida l concentration before the study. Baseline electrocorticography over the su rface of the temporal lobe and depth electrode recordings in the amygdala a nd hippocampus were obtained, followed by 10 min of recording before and af ter the IV administration of both alfentanil 50 mu g/kg and fentanyl 10 mu g/kg. Any changes in cardiovascular Variables were documented. The number o f interictal epileptiform spikes at the most active site for each patient w as tabulated before and after the administration of each drug. Both alfenta nil and fentanyl induced an increase in spike activity in all patients. Alf entanil was more potent, increasing the median number of spikes per epoch f rom 18 to 58, compared with fentanyl (20 to 42 spikes) (P < 0.05). Alfentan il had a shorter duration of action (4.9 +/- 1.3 min) compared with fentany l (8.5 +/- 2 min) (P < 0.009). in nine patients, the most active site was t he hippocampus or amygdala. There was a decrease in mean blood pressure, bu t only after the administration of alfentanil (P < 0.05). Two patients had electrographic evidence of seizure activity. These opioids can be used to a ssist in the localization of the epileptogenic focus during surgery. Implic ations: Both alfentanil and fentanyl activate epileptiform activity in pati ents with temporal lobe epilepsy. These opioids can be used to assist in th e localization of the epileptogenic focus during surgery.